Transmitter digital-to-analog converter with noise shaping

ABSTRACT

A noise shaping module includes a first addition module that receives an N-bit digital input signal, where N is an integer greater than one. A first filter module generates a first filtered output signal based on an output signal of the first addition module. A truncation module generates an M-bit truncated output signal based on the first filtered output signal, where M is an integer less than N. A second filter module generates a second filtered output signal based on the M-bit truncated output signal. The second filtered output signal is an input to the first addition module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/526,485, filed Sep. 25, 2006, which claims the benefit of U.S.Provisional Application No. 60/777,158, filed Feb. 27, 2006. Thedisclosures of the above applications are incorporated herein byreference.

FIELD

The present invention relates to systems and methods for transmittingsignals to a receiver, and, more specifically, to systems and methodsfor controlling noise levels from a transmitter digital-to-analogconverter.

BACKGROUND

In various communication systems, digital-to-analog converters are usedto convert digital signals to analog signals before transmission.Digital-to-analog converters may introduce quantization noise into theanalog signals—particularly when a large number of signal levels areused. Examples of techniques that utilize a large number of outputlevels include Tomlinson-Harashima-Precode and advance modulationschemes such as OFDM and discreet multi-tone modulation.

Typically, to reduce the effect of quantization noise on systemperformance, a power spectrum density (PSD) level of the quantizationnoise should be below a predetermined PSD level of unavoidable noises. Atypical requirement is for the quantization noise to have a PSD that is10 decibels below the PSD of unavoidable noises. Examples of unavoidablenoises include additive white Gaussian noise (AWGN), alien cross-talkfrom other cables or transmitters and quantization noise of the analogto digital converter at the receiver.

Conventional digital-to-analog converter designs produce a quantizationnoise with a white PSD evenly distributed among all frequencycomponents. However, the communication system performance is oftenlimited by a worst case channel. The frequency response of this channelvaries significantly within the transmission bandwidth. As a result, thequantization noise from the transmitter digital-to-analog converter maybe shaped by the channel and observed by the receiver.

The peak of the quantization noise PSD (shaped by the channel) observedby the receiver must be lower than other noises by a predeterminedlevel. As a result, a large number of bits may be required for thedigital-to-analog converter input and the digital-to-analog convertersize and complexity are increased. Reducing the size and complexity of adigital-to-analog converter would lower the overall cost of the system.

Referring now to FIG. 1, a transmitter 8 having an input 10 from anadvance modulation scheme or a pre-coding scheme is illustrated. Theinput 10 generates an N-bit digital input to a truncation module 12. Thetruncation module 12 truncates the N-bit signal to an M-bit signal,where M is an integer less than N. The truncation module 12 eliminatesthe least significant bits from the N-bit digital input signal. TheM-bit signal is provided to a digital-to-analog converter 14 where it isconverted to an analog output signal corresponding to the M-bit signal.

Referring now to FIG. 2, a signal model illustrating the input signala_(n), which corresponds to the output of the truncation module 12, issummed with truncation noise q_(n) at a summing module 16. Thetruncation noise q_(n) is inherent in the truncation module 12. Thetruncation noise is sometimes referred to as quantization noise.

Referring now to FIG. 3, a 10GBASE-T transmitter 20 having a pre-coder18 is illustrated. An input signal a_(k) is provided to a summing module22, the addition module 22 generates a summed signal d_(k) as will bedescribed below. The signal d_(k) is provided to a modulo operationmodule 24 where it is converted to a signal s_(k) that has N-bits.Feedback of the signal s_(k) is provided through a feedback filter 26having a transfer function P(z). The output of the feedback filter 26 isprovided to the addition module 22. Referring back to modulo operationmodule 24, the N-bit signal, s_(k) is provided to the truncation module28, which truncates the signal to an M-bit signal that is provided tothe digital-to-analog converter 32 conversion to an analog signal. Thedigital-to-analog converter 32 illustrated in FIG. 3 may be implementedwith Tomlinson-Harashima-Precode (THP). The approach illustrated inFIGS. 1-3 has quantization noise problems that degrade the performanceof the communication system.

SUMMARY

A noise shaping module includes a first addition module that receives adigital input signal, a first filter module that generates a firstfiltered output signal based on an output of the first addition module,a truncation module that generates a truncated output signal based onthe first filtered module. A second filter module that generates asecond filtered output based on the truncated output signal. The secondfiltered output signal is an input to the first addition module.

A feature of the noise shaping module is that it may be incorporatedinto a system that includes a digital-to-analog converter module thatconverts the truncated output signal to an analog signal. The system mayalso communicate the analog signal of the digital-to analog converteracross a communication channel.

The first filter module of the noise shaping module may also have afirst transfer function and the second filter module may have a secondtransfer function, wherein a sum of the first transfer function and thesecond transfer function is approximately 1.

Another feature of the noise shaping module is that the filtered outputx_(n) is equal to

${{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}},$where G(z) is the first transfer function, H(z) is the second transferfunction, q_(n) is a quantization noise from the truncation module anda_(n) is the digital input signal.

Another feature is that the noise shaping module may include a firsttransfer function that suppress quantization noise from the truncationmodule. The first transfer function may also be a function of acommunication channel characteristic. The communication channelcharacteristic may have a first frequency band having a firstattenuation level and a second frequency band having a secondattenuation level that is greater than the first attenuation level. Thefirst transfer function may suppresses a quantization noise from thetruncation module more in the first frequency band than the secondfrequency band which may be performed so that a noise component isequalized in a frequency domain.

The communication channel may operate in accordance with 10GBASET.

In a further feature of the disclosure, a method includes receiving adigital input signal at a first addition module, filtering an output ofthe first addition module to form a filtered signal, truncating thefiltered signal to form a truncated signal, filtering the truncatedsignal to form a second filtered signal, and communicating the secondfiltered signal to the first addition module.

Another feature of the method is that the truncated signal may beconverted to an analog signal. The analog signal may be communicatedacross a communication channel.

Another feature of the method is filtering an output of the firstaddition module may be performed according to a first transfer function,and filtering the truncated signal may be performed according to asecond transfer function, wherein a sum of the first transfer functionand the second transfer function is approximately 1.

Another feature is that the second filtered signal x_(n) may be equal to

${{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}},$where G(z) is a first transfer function, H(z) is a second transferfunction, q_(n) is a quantization noise from the truncation module anda_(n) is the digital input signal.

Another feature is that the method may include suppressing quantizationnoise from the truncation module with the first transfer function.

Yet another feature is that the first transfer function is a function ofa communication channel characteristic. The communication channelcharacteristic having a first frequency band may be provided having afirst attenuation level and a second frequency band having a secondattenuation level that is greater than the first attenuation level. Themethod may also include suppressing quantization noise more in the firstfrequency band than the second frequency. This may be performed by usingthe first transfer function so that a noise component is equalized in afrequency domain.

In yet another feature of the invention, a noise shaping module includesreceiving means for receiving a digital input signal at a first additionmodule, first filtering means for filtering an output of the firstaddition module to form a filtered signal, truncating means fortruncating the filtered signal to form a truncated signal, secondfiltering means for filtering the truncated signal to form a secondfiltered signal, and communicating means for communicating the secondfiltered signal to the first addition module.

Another feature of the noise shaping module may be a converting meansfor converting the truncated signal to an analog signal and acommunicating means for communicating the analog signal across acommunication channel.

Another feature of the noise shaping module is that the first filteringmeans may comprise a first transfer function and second filtering meansmay comprise a second transfer function, wherein a sum of the firsttransfer function and the second transfer function is approximately 1.

Another feature is that the noise shaping module is that the secondfiltered signal x_(n) may be equal to

${{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}},$where G(z) is the first transfer function, H(z) is the second transferfunction, q_(n) is a quantization noise from the truncation module anda_(n) is the digital input signal.

In another feature of the noise shaping module, the first transferfunction may comprise means for suppressing quantization noise from thetruncation module.

In yet another feature, the first transfer function of the noise shapingmodule may be a function of a communication channel characteristic. Thecommunication channel characteristic may have a first frequency bandhaving a first attenuation level and a second frequency band having asecond attenuation level that is greater than the first attenuationlevel. The noise shaping module may include suppressing means forsuppressing quantization noise from a truncation module more in thefirst frequency band than the second frequency. This may be performed sothat a noise component is equalized in a frequency domain.

In another embodiment of the disclosure, a noise shaping module includesa first addition module that receives an input signal, a modulooperation module generates a modulo output based on an output of theaddition module, a truncation module that truncates the modulo output,and a feedback filter module that generates a feedback signal that isinput to the first addition module based on the truncated output.

A feature of the noise shaping module is that it may be incorporatedinto a system that includes a digital-to-analog converter module thatconverts the truncated output signal to an analog signal. The system mayalso communicate the analog signal of the digital-to analog converteracross a communication channel.

Another feature is that the feedback filter of the noise shaping modulemay have a first transfer function. The first transfer function maysuppress quantization noise from the truncation signal. The firsttransfer function may be a function of a communication channelcharacteristic. The communication channel characteristic comprisestransmitter and receiver analog filter characteristics. Thecommunication channel characteristic may comprise receiver feed forwardequalizer characteristics.

Another feature is that the noise shaping module may include a firsttransfer function that suppress quantization noise from the truncationmodule. The first transfer function may also be a function of acommunication channel characteristic. The communication channelcharacteristic may have a first frequency band having a firstattenuation level and a second frequency band having a secondattenuation level that is greater than the first attenuation level. Thefirst transfer function may suppresses a quantization noise from thetruncation module more in the first frequency band than the secondfrequency band which may be performed so that a noise component isequalized in a frequency domain.

In another feature of the disclosure, a method includes receiving adigital input signal at a first addition module, generating a modulatedoutput based on an output of the addition module, truncating themodulated output to form a truncated signal, and filtering the truncatedsignal to generate a feedback signal that is an input to the firstaddition module based on truncated signal.

One feature is that the truncated signal may be converted to an analogsignal. Another feature is that filtering the truncated signal mayinclude filtering the truncated signal with a filter having a firsttransfer function.

Another feature is that the method may include suppressing quantizationnoise from the truncation signal with the first transfer function. Thefirst transfer function may be a function of a communication channelcharacteristic such as a transmitter and receiver analog filtercharacteristics or receiver feed forward equalizer characteristics.

Another feature of the method is the method may include providing thefirst transfer function as a function of a communication channel havinga first frequency band with a first attenuation level and a secondfrequency band with a second attenuation level that is greater than thefirst attenuation level.

Another feature is that the method may also include suppressing aquantization noise more in the first frequency band than the secondfrequency band with the first transfer function. This may be performedso that a noise component is equalized in a frequency domain with thefirst transfer function.

In yet another feature of the disclosure, a noise shaping moduleincludes receiving means for receiving a digital input signal at a firstaddition module, generating means for generating a modulated outputbased on an output of the addition module, truncating means fortruncating the modulated output to form a truncated signal, andfiltering means for filtering the truncated signal to generate afeedback signal that is input to the first addition module based on thetruncated signal.

Another feature of the noise shaping module may include a convertingmeans for converting the truncated signal to an analog signal.

A feature of the filtering means may include filtering means forfiltering the signal with a filter having a first transfer function.

Another feature of the noise shaping module includes may be theinclusion of suppressing means for suppressing quantization noise fromthe truncation module with the first transfer function.

Another feature of the noise shaping module may include providing meansfor providing the first transfer function as a function of acommunication channel characteristic.

Another feature of the noise shaping module may include providing meansfor providing the communication channel characteristic as a function oftransmitter and receiver analog filter characteristics.

Another feature of the noise shaping module may include providing meansfor providing the communication channel characteristic as a function ofthe receiver feed forward equalizer characteristics.

Another feature of the noise shaping module may include providing meansfor providing the first transfer function as a function of acommunication channel having a first frequency band with a firstattenuation level and a second frequency band with a second attenuationlevel that is greater than the first attenuation level.

Another feature of the noise shaping module may include suppressingmeans for suppressing quantization noise more in the first frequencyband than the second frequency band with the first transfer function.

Another feature of the noise shaping module may include suppressingmeans for suppressing a quantization noise from the truncation modulemore in the first frequency band than the second frequency band so thata noise component is equalized in a frequency domain with the firsttransfer function.

In another embodiment of the disclosure, a noise shaping module includesa first addition module that receives a digital input signal andgenerates an output signal, a truncation module that generates atruncated output signal based on an output of said first additionmodule; and a filter module that generates a filtered output based on acombination of output signal of the first addition module and thetruncated output signal of the first truncation module.

A feature of the noise shaping module is that it may be incorporatedinto a system that includes a digital-to-analog converter module thatconverts the truncated output signal to an analog signal. The system mayalso communicate the analog signal of the digital-to analog converteracross a communication channel.

Another feature is that the first filter module may include a firsttransfer function. The first transfer function may be a function of acommunication channel characteristic having a first frequency band witha first attenuation level and a second frequency band with a secondattenuation level that is greater than the first attenuation level. Thefirst transfer function may be is 1+F(z).

Another feature is that the noise shaping module may include a firsttransfer function that suppress quantization noise from the truncationmodule. The first transfer function may also be a function of acommunication channel characteristic. The communication channelcharacteristic may have a first frequency band having a firstattenuation level and a second frequency band having a secondattenuation level that is greater than the first attenuation level. Thefirst transfer function may suppresses a quantization noise from thetruncation module more in the first frequency band than the secondfrequency band which may be performed so that a noise component isequalized in a frequency domain.

In another feature of the disclosure a method includes receiving adigital input signal at a first addition module, truncating an output ofthe first addition module to form a truncated signal, and filtering thecombination of an output of the first addition module and an the firsttruncated module to form a filtered output signal, and adding thefiltered output signal to the input signal.

One feature of the method includes converting the truncated outputsignal to an analog signal. The analog signal may then be communicatedthrough a communication channel.

Another feature of the method includes providing the filter module witha first transfer function. The first transfer function may be a functionof a communication channel having a first frequency band with a firstattenuation level and a second frequency band with a second attenuationlevel that is greater than the first attenuation level.

Another feature of the method includes suppressing a quantization noisefrom the truncated signal more in the first frequency band than thesecond frequency band.

Another feature of the method may include suppressing a quantizationnoise from the truncated signal more in the first frequency band thanthe second frequency band so that a noise component is equalized in afrequency domain.

In a further feature of the disclosure, a noise shaping module includesreceiving means for receiving a digital input signal at a first additionmodule, truncating means for truncating an output of the first additionmodule to form a truncated signal, filtering means for filtering acombination of an output of the first addition module and an output ofthe first truncation module to form a filtered output signal, and addingmeans for adding the filtered output signal to the input signal.

One feature of the noise shaping module includes means for providing thefilter means with a first transfer function comprises means forproviding the first transfer function as a function of a communicationchannel having a first frequency band with a first attenuation level anda second frequency band with a second attenuation level that is greaterthan the first attenuation level.

Another feature of the means for providing the first transfer functionof the noise shaping module includes suppressing means for suppressing aquantization noise from a truncation means more in the first frequencyband than the second frequency band.

Another feature of the means for providing the first transfer functionof the noise shaping module includes suppressing means for suppressing aquantization noise from the truncation means more in the first frequencyband than the second frequency band so that a noise component isequalized in a frequency domain.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of a prior art transmitter.

FIG. 2 is a signal model of the transmitter of FIG. 1.

FIG. 3 is a functional block diagram of a second prior art transmitterdesign.

FIG. 4 is a functional block diagram of a transmitter design accordingto a first embodiment of the present disclosure.

FIG. 5 is a functional block diagram of a transmitter design accordingto a second embodiment of the present disclosure.

FIG. 6 is a signal model of the block diagram of FIG. 4.

FIG. 7 is a functional block diagram of a third transmitter according tothe present disclosure.

FIG. 8A is a functional block diagram of a computing device;

FIG. 8B is a functional block diagram of a high definition television;

FIG. 8C is a functional block diagram of a vehicle control system;

FIG. 8D is a functional block diagram of a cellular phone;

FIG. 8E is a functional block diagram of a set top box; and

FIG. 8F is a functional block diagram of a media player.

DETAILED DESCRIPTION

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the disclosure,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module, circuit and/or device refers to anApplication Specific Integrated Circuit (ASIC), an electronic circuit, aprocessor (shared, dedicated, or group) and memory that execute one ormore software or firmware programs, a combinational logic circuit,and/or other suitable components that provide the describedfunctionality. As used herein, the phrase at least one of A, B, and Cshould be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

The present disclosure provides a system for use with a transmitter. Thetransmitter may be any type of transmitter including wired transmitters,wireless transmitters, and various other types of transmitters.

Referring now to FIG. 4, a transmitter module 60 is illustrated havingan input 70. Input 70 may provide an input from an advanced modulationscheme or a pre-coding scheme as described above. The input 70 providesan N-bit digital input to a noise-shaping module 72. The noise-shapingmodule 72 provides an M-bit signal to a digital-to-analog convertermodule 74 that provides an analog output to a communication channel 76.The communication channel 76 provides the analog signal to a receiver78. The communication channel 76 may be a two-way channel as will bedescribed below.

Noise-shaping module 72 includes a first addition module 80 and atruncation module 84. A second addition module 86 receives an output ofthe truncation module 84 and the input of the truncation module 84 oroutput of the first addition module 80 and provides the difference to afirst filter module 88. The first filter module has a transfer functionF(z). The output of the first filter module is communicated to theaddition module 80. The output of the truncation module 84 is an M-bitsignal, where M is an integer less than N. The truncation module 84removes the least significant bit or bits from the N-bit digital input.The output of the truncation module 84 is fed to the digital-to-analogconverter 74.

The signal through the noise shaping circuit is undistorted, while thequantization noise added by the truncation module 84 is passed to thedigital-to-analog converter with an overall transfer function of 1+F(z).

From the receiving end, a channel processed version of the output signalx_(n) and the digital-to-analog converter quantization noise is given byC(z)*(1+F(z))*q_(n), where C(z) is the transfer function of thecommunication channel. The transfer function F(z) may vary depending onthe particular system to which the present invention is applied. F(z) isdesigned so that the quantization noise q_(n) is suppressed in thefrequency band where the attenuation of C(z) is small, and less in thefrequency band where C(z)'s attenuation is large. At the receiving end,the digital-to-analog converter quantization noise component isequalized in the frequency domain and has a much smaller power comparedto the receiving quantization noise power with the same bit numberconventional digital-to-analog converter implemented at the transmitter.

Referring now to FIG. 5, a transmitter module 100 is illustrated havingan input 110. Input 110 may provide an input from an advanced modulationscheme or a pre-coding scheme as described above. The input 110 providesan N-bit digital input to a noise-shaping module 112. The noise-shapingmodule 112 provides an M-bit signal to a digital-to-analog convertermodule 114 that provides an analog output to a communication channel116. The communication channel 116 provides the analog signal to areceiver 118. The communication channel 116 may be a two-way channel aswill be described below.

Noise-shaping module 112 includes an addition module 130, a first filtermodule 132, a truncation module 134, and a second filter module 136. Theaddition module 130 sums the output of the second filter module 136 andthe N-bit digital input 110. The N-bit digital input 110 with feedbackfrom the second filter module 136 is communicated through the firstfilter module 132. The first filter module 132 has a transfer functionH(z) that is a function of the communication channel. The digital outputof the filter module 132 is communicated to the truncation module 134.The output of the truncation module 134 is an M-bit signal, where M isan integer less than N. The truncation module 134 removes the leastsignificant bit or bits from the N-bit digital input. The output of thetruncation module 134 is communicated to the digital-to-analog converter114. The output of the truncation module 134 is also provided to thesecond filter 136.

Referring now to FIG. 6, a signal model of the noise-shaping module 112of FIG. 5 is set forth. The digital input to the addition module 130 isset forth as input signal a_(n). The first filter 132 and the secondfilter 136 have the transfer functions described above. However, theoutput of the noise-shaping module 112 also includes truncation noisedenoted by the signal q_(n). The truncation noise is inherent in thetruncation module 134. Minimizing the effect of the truncation noise onthe receiver is a desired goal of the disclosure. The truncation noiseis illustrated by the signal q_(n) provided to an addition module 140.The addition module 140 is part of the signal model and not part of thephysical device. The output signal is denoted by x_(n). Thus, the outputsignal x_(n) is equal to

$x_{n} = {{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}}$

It should be noted that the signal a_(n) may be passed throughnoise-shaping module 112 undistorted when H(z)+G(z)=1. When the aboveconditions are satisfied, the noise component in the output signal x_(n)is given by H(z)*q_(n). Therefore, the transfer function H(z) controlsthe frequency of the digital-to-analog converter quantization noiseq_(n).

From the receiving end, a channel process version of this output signalx_(n) and the digital-to-analog converter quantization noise is given byC(z)*H(z)*q_(n), where C(z) is the transfer function of thecommunication channel. The transfer functions G(z) and H(z) may varydepending on the particular system to which the present invention isapplied. H(z) is designed so that the quantization noise q_(n) issuppressed in the frequency band where C(z)'s attenuation is small, andless in the frequency band where C(z)'s attenuation is large. At thereceiving end, the digital-to-analog converter quantization noisecomponent is equalized in the frequency domain and has a much smallerpower compared to the receiving quantization noise power with the samebit number conventional digital-to-analog converter implemented at thetransmitter.

The present disclosure utilizes knowledge of the communication channelfrequency response in the transmitter digital-to-analog converterdesign. The first filter 132 and second filter 136 are designed toclosely match the channel frequency's response so that the receiver sidedigital-to-analog converter quantization noise peak is minimized.

It should be noted that over-sampling is unnecessary to perform noiseshaping although it may be used. The noise shaping provided in thepresent disclosure is within the signal band so that the receiver endquantization noise is equalized. It should also be noted that thedigital filters may be implemented at the symbol rate.

Referring now to FIG. 7, a 10GBASE-T transmitter 200 having anoise-shaping module 202 is illustrated. FIG. 7 is provided in contrastto FIG. 3. That is, FIG. 7 has feedback provided in a different locationand a different feedback transfer function than the circuit of FIG. 3.In this embodiment, the feedback filter has a transfer function P(z)with similar goals to the first filter and second filter described abovein FIGS. 5 and 6. The 10GBASE-T standard adopts theTomlinson-Harashima-Precoding (THP) configuration in which coefficientsare exchanged between a receiver 210 and the transmitter 200 using atwo-way communication channel 208. This allows the transfer functionP(z) of the feedback filter 226 to match the channel characteristicscombined with the transmitter/receiver analog filters and receiver feedforward equalizer. The transfer function P(z) will vary depending uponthe particular system to which it is applied.

The output of the feedback filter 226 is communicated to addition module22. The output of the addition module 22 is communicated to the modulooperation module 24 in a similar manner to FIG. 3 above. The output ofthe modulo operation module 24, s_(k), is communicated to truncationmodule 28. The truncated M-bit signal is communicated todigital-to-analog converter 30 and to feedback filter 226. The output ofthe digital-to-analog converter 30 is provided to the receiver 210.

As mentioned above, the receiver 210 may communicate with thetransmitter 200 to provide the coefficients and characteristics throughcommunication channel 208. After exchanging the characteristics, thetransfer function P(z) may be formed. The transfer function may beformed once for a particular system or many times for a system that maybe coupled to various types of receivers or various communications thatmay have various communication channel characteristics such as differentcable lengths. Often times, such a system may be designed for the worstcase characteristic such as the longest cable length.

According to THP configuration, P(z) is automatically adjusted such thatC(z)/(1+P(z)) is equalized. Hence, 1/(1+P(z)) is the desired transferfunction by which the truncation quantization noise shall be shaped.

The module 202 shapes the truncation noise by 1/(1+P(z)). And thereceiving end truncation noise is minimized.

It should also be noted that a similar configuration to that describedwith respect to FIGS. 4, 5 and 6 may be adopted in a 10GBASE-Ttransmitter. However, because the feedback filter is provided, asimpler, more attractive structure is utilized as set forth in FIG. 7.

Referring now to FIGS. 8A-8F, various exemplary implementations of thedevice are shown. Referring now to FIG. 8A, a computer device 400 isillustrated. The device may implement and/or be implemented in atransmitter DAC of a local area network (LAN) transmitter 404. In someimplementations, the signal processing and/or control circuit 402 and/orother circuits (not shown) in the computer device 400 may process data,perform coding and/or encryption, perform calculations, and/or formatdata that is output to and/or received from a magnetic storage medium406. As illustrated, the transmitter may be part of a LAN transmitter404. The LAN transmitter 404 may be wired or wireless.

The computer device 400 may be connected to memory 409 such as randomaccess memory (RAM), low latency nonvolatile memory such as flashmemory, read only memory (ROM) and/or other suitable electronic datastorage.

Referring now to FIG. 8B, the device can be implemented in a transmitterof a wireless or wired LAN 429 of a high definition television (HDTV)420. The HDTV 420 receives HDTV input signals in either a wired orwireless format and generates HDTV output signals for a display 426. Insome implementations, signal processing circuit and/or control circuit422 and/or other circuits (not shown) of the HDTV 420 may process data,perform coding and/or encryption, perform calculations, format dataand/or perform any other type of HDTV processing that may be required.

The HDTV 420 may communicate with a mass data storage 427 that storesdata in a nonvolatile manner such as optical and/or magnetic storagedevices. The HDTV 420 may be connected to memory 428 such as RAM, ROM,low latency nonvolatile memory such as flash memory and/or othersuitable electronic data storage. The HDTV 420 may support connectionswith a LAN via a LAN network interface 429 utilizing the transmittercapabilities described above. The LAN network interface 429 may bewireless or wired.

Referring now to FIG. 8C, the device may be implemented in a wired orwireless WLAN interface 440 of a control system of a vehicle 430. Insome implementations, the device may be implemented in a powertraincontrol system 432 that receives inputs from one or more sensors such astemperature sensors, pressure sensors, rotational sensors, airflowsensors and/or any other suitable sensors and/or that generates one ormore output control signals such as engine operating parameters,transmission operating parameters, and/or other control signals.

The control system 440 may likewise receive signals from input sensors442 and/or output control signals to one or more output devices 444. Insome implementations, the control system 440 may be part of an anti-lockbraking system (ABS), a navigation system, a vehicle telematics system,a lane departure system, an adaptive cruise control system, a vehicleentertainment system such as a stereo or video system, and the like.Still other implementations are contemplated.

The powertrain control system 432 may also communicate with mass datastorage 446 that stores data in a nonvolatile manner. The mass datastorage 446 may include magnetic storage devices for example hard diskdrives HDD. The powertrain control system 432 may be connected to memory447 such as RAM, ROM, low latency nonvolatile memory such as flashmemory and/or other suitable electronic data storage. The powertraincontrol system 432 also may support connections with a wired or wirelessLAN via a LAN network interface 448. A wired connection would besuitable for use in a diagnostic capacity while servicing the vehicle.

Referring now to FIG. 8D, the device can be implemented in a wirelesslocal area network interface 468 of a cellular phone 450. The phone 450may include a cellular antenna 451. In some implementations, thecellular phone 450 includes a microphone 456, an audio output 458 suchas a speaker and/or audio output jack, a display 460 and/or an inputdevice 462 such as a keypad, pointing device, voice actuation and/orother input device. The signal processing and/or control circuits 452and/or other circuits (not shown) in the cellular phone 450 may processdata, perform coding and/or encryption, perform calculations, formatdata and/or perform other cellular phone functions.

The cellular phone 450 may communicate with mass data storage 464 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices, for example, a hard disk drive HDD. The cellular phone450 may be connected to memory 466 such as RAM, ROM, low latencynonvolatile memory such as flash memory and/or other suitable electronicdata storage. The cellular phone 450 also may support connections with aWLAN via the WLAN interface 468 using the transmitter technologydescribed above.

Referring now to FIG. 8E, the device can be implemented in a wired orwireless LAN interface 496 of a set top box 480. The LAN interface 496may include the transmitter corresponding to the above embodiments. Theset top box 480 receives wired or wireless signals from a source 481such as a broadband source and outputs standard and/or high definitionaudio/video signals suitable for a display 488 such as a televisionand/or monitor and/or other video and/or audio output devices. Thesignal processing and/or control circuits 484 and/or other circuits (notshown) of the set top box 480 may process data, perform coding and/orencryption, perform calculations, format data and/or perform any otherset top box function.

The set top box 480 may communicate with mass data storage 490 thatstores data in a nonvolatile manner. The mass data storage 490 mayinclude optical and/or magnetic storage devices for example hard diskdrives HDDs. The set top box 480 may be connected to memory 494 such asRAM, ROM, low latency nonvolatile memory such as flash memory and/orother suitable electronic data storage.

Referring now to FIG. 8F, the device can be implemented in a wired orwireless LAN interface of a media player 500. In some implementations,the media player 500 includes a display 507 and/or a user input 508 suchas a keypad, touchpad and the like. In some implementations, the mediaplayer 500 may employ a graphical user interface (GUI) that typicallyemploys menus, drop down menus, icons and/or a point-and-click interfacevia the display 507 and/or user input 508. The media player 500 furtherincludes an audio output 509 such as a speaker and/or audio output jack.The signal processing and/or control circuits 504 and/or other circuits(not shown) of the media player 500 may process data, perform codingand/or encryption, perform calculations, format data and/or perform anyother media player function.

The media player 500 may communicate with mass data storage 510 thatstores data such as compressed audio and/or video content in anonvolatile manner. In some implementations, the compressed audio filesinclude files that are compliant with MP3 format or other suitablecompressed audio and/or video formats. The media player 500 may beconnected to memory 514 such as RAM, ROM, low latency nonvolatile memorysuch as flash memory and/or other suitable electronic data storage. Themedia player 500 also may support connections with a wired or wirelessLAN via a LAN network interface 516 using the transmitter moduledescribed above in FIGS. 4-6. Still other implementations in addition tothose described above are contemplated.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A noise shaping module comprising: a first addition module thatreceives an N-bit digital input signal, wherein N is an integer greaterthan one; a first filter module that generates a first filtered outputsignal based on an output signal of the first addition module; atruncation module that generates an M-bit truncated output signal basedon the first filtered output signal, wherein M is an integer less thanN; and a second filter module that generates a second filtered outputsignal based on the M-bit truncated output signal, wherein the secondfiltered output signal is an input to the first addition module.
 2. Thenoise shaping module of claim 1, wherein the truncation module truncatesat least one least significant bit (LSB) of the N-bit digital inputsignal to generate the M-bit truncated output signal.
 3. A systemcomprising the noise shaping module of claim 1, the system furthercomprising: a digital-to-analog converter module that converts the M-bittruncated output signal to an analog signal.
 4. The noise shaping moduleof claim 1, wherein: the first filter module has a first transferfunction; the second filter module has a second transfer function; and asum of the first transfer function and the second transfer function isapproximately
 1. 5. The noise shaping module of claim 4, wherein thesecond filtered output signal is equal to:${{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}},$wherein G(z) is the first transfer function, H(z) is the second transferfunction, q_(n) is a quantization noise from the truncation module anda_(n) is the N-bit digital input signal.
 6. The noise shaping module ofclaim 4, wherein the first transfer function of the first filter modulereduces quantization noise from the truncation module.
 7. The noiseshaping module of claim 4, wherein the first transfer function is basedon a characteristic of a communication channel.
 8. The noise shapingmodule of claim 7, wherein the communication channel characteristic hasa first frequency band having a first attenuation level and a secondfrequency band having a second attenuation level that is greater thanthe first attenuation level.
 9. The noise shaping module of claim 8,wherein the first transfer function reduces quantization noise from thetruncation module in the first frequency band more than in the secondfrequency band.
 10. The noise shaping module system of claim 7, whereinthe communication channel operates in accordance with 10GBASET.
 11. Amethod comprising: generating a first output signal based on an N-bitdigital input signal, wherein N is an integer greater than one;filtering the first output signal to generate a first filtered outputsignal; truncating the first filtered output signal to an M-bittruncated output signal based, wherein M is an integer less than N;filtering the M-bit truncated output signal to generate a secondfiltered output signal; and generating the first output signal furtherbased on the second filtered output signal.
 12. The method of claim 11,wherein the truncating the first filtered output signal includestruncating at least one least significant bit (LSB) of the N-bit digitalinput signal to generate the M-bit truncated output signal.
 13. Themethod of claim 11, further comprising converting the M-bit truncatedoutput signal to an analog signal.
 14. The method of claim 11, wherein:filtering the first output signal includes filtering the first outputsignal based on a first transfer function; and filtering the M-bittruncated output signal includes filtering the M-bit truncated outputsignal based on a second transfer function, wherein a sum of the firsttransfer function and the second transfer function is approximately 1.15. The method of claim 14, wherein the second filtered output signal isequal to:${{\frac{1}{{G(z)} + {H(z)}}a_{n}} + {\frac{H(z)}{{G(z)} + {H(z)}}q_{n}}},$wherein G(z) is the first transfer function, H(z) is the second transferfunction, q_(n) is a quantization noise from the truncating of the firstfiltered output signal and a_(n) is the N-bit digital input signal. 16.The method of claim 14, wherein the first transfer function reducesquantization noise from the truncating of the first filtered outputsignal.
 17. The method of claim 14, wherein the first transfer functionis based on a characteristic of a communication channel.
 18. The methodof claim 17, wherein the communication channel characteristic has afirst frequency band having a first attenuation level and a secondfrequency band having a second attenuation level that is greater thanthe first attenuation level.
 19. The method of claim 18, wherein thefirst transfer function reduces quantization noise from the truncatingin the first frequency band more than in the second frequency band. 20.The method of claim 17, wherein the communication channel operates inaccordance with 10GBASET.